Wide-eyed Wonder: an artist's musings on three-dimensional vision

Some are color blind. I am stereo blind.

3D Movies and Stereoblindess

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Hi, I’m just curious … I don’t see 3D. Would it be possible for me to get a glimpse of your 3D movie and find out what I can see?

I asked this only after purchasing tickets for the 2D version of Narnia: The Voyage of the Dawntreader Afterward, I and my friends shared a pair of glasses to briefly check out the 3D difference.

Even though I didn’t get the “Wow!” of an object jumping off the screen or moving behind the screen that my friends saw, I would still pay the extra bit to see the richness of detail the new polarized glasses create. Everything was clear, and not a blur (which happened often in the 2d version. Thoughts on why later.)

With polarization, which cuts out some glare, I saw deeper colors. [1] I studied the golden shell Edmund pulled from the pool of gold, and it appeared richer to me, even though it was not 3D. Instead, it was similar to what I experience when I see a painting by that rare artist that can translate 3D to a canvas, such as my friend and portrait artist Judith Carducci.

Unlike legacy 3d movies that required the red-cyan glasses, the new technology uses a different kind of fusion. Legacy film 3D required two projectors running film perfectly in synch, shot with cameras that had to be aligned according to a precise geometric formula during filming. [2] One camera filmed through a cyan filter, and the other filmed through a red filter. The red-cyan glasses worn by viewers would cancel out the conflicting image and the binocular function in the brain’s visual cortex would fuse the two images from each eye to create 3D. [3] It was an imprecise method and never caught on, as every imperfection would create literal headaches.

Furthermore, the stereoblind, who could not bring the non-conflicting images together with one-eyed viewing, experienced a movie that was either completely red or cyan!

The new technologies are digital. No film is used. The two cameras that do the “filming” to digital files are precisely aligned with a computer. [4] Digital post processing of CGI effects is also rendered with 3D formulas. (In the case of Dawn Treader, only the post processing was 3D. Two cameras were not used to shoot the live action. [5]) The left and right integrated “film” file is shown through only one projector, as the input from both angles is digitally fused into one movie. [4]

Both RealD and Dolby 3D projection systems use a rotating high-speed alternating filter. Left and right images alternate so quickly that the brain takes them in through the Dolby optically coated or RealD polarized glasses as one continuous image. The coatings or polarization in the glasses cancel out the conflicting alternate images in each lens. [6] [7]

What this means for the steroblind is only every other image is seen through either the right lens or the left. There is no haloing or ghosting because the opposite image is blocked by the same lens the dominant eye is using.

This is good news! No ghosting! No red or cyan viewing!

Eye problems, even with the 2D version

The newer 3D movies rely on extraordinary optical flow and motion parallax. The rapid CGI rotation and camera panning appeared blurred or jerky to me in the 2D version, annoyingly so, because all my depth cues were put on steroids. It was like watching a home video where the would-be videographer didn’t know how to pan his camera. If these scenes had lasted any length of time, I would have needed to avert my eyes to avoid nausea, a common problem I experience due to lack of stereoscopic ability.

All of the film’s CGI sequences appeared jerky, like watching a video with a slow internet connection. At the end of the film, during the credits, the background had a very annoying flicker. I wonder if this is because the producer did not bother to create alternate 2D CGI? The film underwent 8 months of 3D post processing. [5] Making alternate 2D CGI sequences may not have been in the budget, especially if the producers thought the 3D ghosting or haloing and alternating flicker would not be noticeable to most viewers.

Secondly, much of the film was was shot with a lack of depth of field, especially during the layered action scenes onboard the ship. Because I am steroblind, relative size relationships and perspective behind and before the action were out of focus. I felt somewhat lost and annoyed without these depth cues, as I was constantly subconsciously attempting to bring the whole scene into focus.


In this image, Lucy’s face is in focus, but the painting and Edmund are not. This is due to the way the scene was shot, with a lack of depth of field.

All this points to a dim future for the stereoblind movie-goer, as every 2D version of a 3D movie is not going to be as easy to watch as the simple 2D movies of old.

RealD polarized or Dolby coated glasses would cancel out any 3D flicker that may be embedded in a 2D version, but how to find out if 3D sequences are in the movie? Would the ticket person be able to hand out the glasses for 2D movies if asked? Probably not. Better to spend the extra 3 bucks and just watch the 3D version with the same flatness I see in real life.

At least I am improving my peripheral awareness to enjoy the pumped-up optic flow and motion parallax that these new films are dishing out.

Links to the technology of 3d movies for further exploration

Popular Mechanics “The Tech Behind 3D’s Big Revival” April 2009 http://popularmechanics.com

“JDSU Shares Science Behind 3D” http://www.youtube.com JDSU is the company that developed the coatings for Dolby 3D. The commentator offers some lame misinformation, as his competitor’s polarized glasses are being recycled at movie theaters and not thrown into landfills.

“To 3D Or Not To 3D: Buy The Right Chronicles Of Narnia Ticket” http://www.cinemablend.com offers a sub-par 3D analysis of the film, as the reviewer says at one point that it didn’t matter if she saw the film with the polarized glasses or not. I’m sorry, but in any 3D film, the glasses cut out the bothersome ghosting. This reviewer must have grown up with poor TV reception in West Virginia.

Tech info on RealD from wikipedia

RealD 3D cinema technology uses circularly polarized light to produce stereoscopic image projection. Circular polarization technology has the advantage over linear polarization methods in that viewers are able to tilt their head and look about the theater naturally without a disturbing loss of 3D perception, whereas linear polarization projection requires viewers to keep their head orientation aligned within a narrow range of tilt for effective 3D perception; otherwise they may see double or darkened images.[2]

The high-resolution, digital cinema grade video projector alternately projects right-eye frames and left-eye frames 144 times per second.[2] The projector is either a Texas Instruments’ Digital Light Processing device or Sony’s reflective liquid crystal display. A push-pull electro-optical liquid crystal modulator called a ZScreen is placed immediately in front of the projector lens to alternately polarize each frame. It circularly polarizes the frames clockwise for the right eye and counterclockwise for the left eye. The audience wears spectacles with oppositely circularly polarized lenses to ensure each eye sees only its designated frame, even if the head is tilted. In RealD Cinema, each frame is projected three times to reduce flicker, a system called triple flash. The source video is usually produced at 24 frames per second per eye (total 48 frames/s), which may result in subtle ghosting and stuttering on horizontal camera movements. A silver screen is used to maintain the light polarization upon reflection and to reduce reflection loss to counter the inherent losses by the polarization filters. The result is a 3D picture that seems to extend behind and in front of the screen itself.[3]

Tech info on Dolby 3D from wikipedia

Dolby 3D uses a Dolby Digital Cinema projector that can show both 2D and 3D films. For 3D presentations, an alternate color wheel is placed in the projector. This color wheel contains one more set of red, green, and blue filters in addition to the red, green, and blue filters found on a typical color wheel. The additional set of three filters are able to produce the same color gamut as the original three filters but transmit light at different wavelengths. Glasses with complementary dichroic filters in the lenses are worn which filter out either one or the other set of three light wavelengths. In this way, one projector can display the left and right stereoscopic images simultaneously. This method of stereoscopic projection is called wavelength multiplex visualization. The dichroic filters in the Dolby 3D glasses are more expensive and fragile than the glasses technology used in circular polarization systems like RealD Cinema and are not considered disposable. However, an important benefit of Dolby 3D as compared to RealD is that no special silver screen is needed for it to work.

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